Synthesis and structural studies of copper(II), nickel(II) and cobalt(II) complexes of a 14-membered trans-N2S2 dibenzo macrocycle with two pendant pyridylmethyl groups

Abstract

The 8,17-bis(2-pyridylmethyl)-functionalised derivative (L²) of a 14-membered trans-N₂S₂ dibenzo macrocycle 6,7,8,9,15,16,17,18-octahydrodibenzo[f,m][1,8,4,11]dithiadiazacyclotetradecine has been prepared and its crystal structure determined. The ligand L² forms stable complexes with nickel(II)1, copper(II)2 and cobalt(II)3. The complexes have been isolated in the solid state and characterised by standard methods and single-crystal X-ray diffraction. Crystal data for L²: space group P2₁/c, a= 945.6(1), b= 1467.9(2), c= 1041.1(2) pm, β= 115.67(1)°, Z= 2, R(R′)= 0.035(0.040) for 2183 observed reflections. Complex 1: space group P2₁/n, a= 1418.8(3), b= 1288.8(3), c= 1867.0(4) pm, β= 109.20(3)°, Z= 4, R(R′)= 0.067(0.068) for 4124 observed reflections. The nickel atom lies outside the macrocyclic cavity and is in a distorted octahedral cis-N₄S₂ environment. Complex 2: space group P, a= 787.8(2), b= 1137.5(2), c= 1800.5(4) pm, α= 98.84(3), β= 99.43(3), γ= 94.74(3)°, Z= 2, R(R′)= 0.082(0.075) for 2165 observed reflections. The copper atom exhibits a highly distorted trigonal-prismatic co-ordination geometry with the following distances: Cu–S, 242.7(4) and 269.8(4), Cu–N(amine) 225.8(11) and 255.2(10) and Cu–N(pyridine) 198.4(11) and 200.2(12) pm, respectively. Complex 3: space group P, a= 789.3(2), b= 1165.8(2), c= 1806.2(3) pm, α= 98.90(1), β= 98.86(2), γ= 94.24(2)°, Z= 2, R(R′)= 0.066(0.063) for 3039 observed reflections. The geometry about high-spin cobalt(II) is trigonal prismatic with average Co–S, Co–N(amine) and Co–N(pyridine) bond lengths of 252.5, 229.0 and 213.7 pm, respectively. The stereochemistry of the free and complexed ligand is discussed with respect to these structures.